Improved uniformity and selected area deposition of diamond by the oxy-acetylene flame method
The role of SiO2 in nucleation of diamond has been investigated in an oxy-acetylene flame. It was found that growth methods that minimize SiO2 formation enchance diamond nucleation. A short pretreatment of a scratched Si surface in a low oxygen-to-acetylene ratio flame, at a distance 1.5 cm from the flame core, significantly improve uniformity of subsequent diamond growth. When scratched surfaces were intentionally oxidized, nucleation of diamond was completely inhibited. By using a mask to controllably deposit SiO2 on a scratched Si surface, highly selective deposition of diamond was achieved with resolution below 5 μm. These results are discussed with reference to competing oxidation and carbon formation processes that take place during the nucleation of diamond. During the nucleation stage, carbon may be deposited on the scratched Si via a route in which the Si surface catalyzes carbon formation reactions that are otherwise kinetically unfavorable. The formation of an oxide layer, on the other hand, would act to passivate the surface, and thus inhibit carbon formation via a catalytic route. The decomposition of CO to C and CO2 is given as an example of a reaction that is favored at temperatures below 1000 K, but requires surface catalysis to proceed because it remains frozen out in the gas phase due to a very slow reaction rate.
Journal of Materials Research
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